First, two police officers accused of raping a drunken woman in her apartment were acquitted. So were the two supervisors charged in connection with the 2007 Deutsche Bank building blaze that killed a pair of firefighters.

Now Vance is looking at the probable collapse of his highest-status case yet: the allegation that Dominique Strauss-Kahn, then head of the International Monetary Fund and a leading candidate for the French presidency, raped a hotel chambermaid.

A judge yesterday freed Strauss-Kahn from his strict house arrest and refunded his multimillion-dollar bail after prosecutors had to admit in court that their star witness has “credibility issues.”

Does she ever.

It turns out the unnamed woman, a native of Guinea who was granted legal asylum, has been lying about pretty much everything since she arrived on these shores — including, most significantly, her account of the alleged rape.

Under oath, she told the grand jury that indicted Strauss-Kahn that she cowered in fear after the attack in the hallway on the 28th floor of the Sofitel New York hotel until he had left the room — and then immediately notified her supervisors.

In fact, embarrassed prosecutors disclosed yesterday, “she proceeded to clean a nearby room and then returned to Suite 2806″ — the alleged crime scene — “and began to clean that suite before she reported the incident.”

Also, just hours after the attack, she phoned a jailed drug dealer and discussed how she could benefit by pressing a case against Strauss-Kahn. The same man is one of several people who’ve made $100,000 in unexplained cash deposits to the woman’s bank account from five different states.

Moreover, investigators have learned that she falsified another sexual attack — a brutal gang rape by soldiers in Guinea — on her asylum application, as well as claiming a phony child as a tax deduction and misrepresenting her income to qualify for subsidized housing.

A not-especially-believable witness, in other words.

This doesn’t automatically mean she wasn’t attacked, of course. And the forensic evidence strongly suggests that some kind of a sexual encounter took place between her and Strauss-Kahn.

But was it consensual? Was it paid for? Did she use the incident to try to extort the prominent Frenchman?

The Post’s Larry Celona and Laura Italiano reported yesterday that emissaries representing Strauss-Kahn traveled to Guinea to meet with her family and tried to broker a settlement that would make the case disappear.

Still, one thing is undeniable — the version that Vance’s prosecutors told in court yesterday stands in sharp contrast to their initial insistence that “the victim provided very powerful details consistent with a violent sexual assault committed by the defendant.”

Which raises the question: What exactly did Vance & Co. know, and when did they know it?

Or not know it, as the case may be.

Certainly, the DA’s office must have known before yesterday’s published accounts that its complaining witness had been gaming them. But Vance wasn’t taking reporters’ questions yesterday.